This application relates to a polycarbonate composition with enhanced properties, particularly as they relate to thin wall flame retardance. This composition can be used in the formation of injection molded or extruded articles.
Polycarbonate has shown excellent adaptability for a wide variety of applications. Numerous additives are known in the art for a variety of purposes, for example to provide flame retardance, to enhance impact strength, and to enhance resistance to degradation resulting from exposure to light and/or chemicals. While each of these additives has a beneficial affect, in many cases this benefit is achieved only at the expense of some other property. Thus, for any given application, careful selection of additives is necessary to achieve the properties needed for that application.
Flame retardance in polycarbonate articles reflects both the burn time of the composition when ignited, and the tendency of the composition to drip molten plastic which can ignite nearby materials. Flame retardance is a function of both the composition of the material and the wall thickness of the article into which the material is formed. Thus, flame retardance is frequently assessed using the rating system of UL94 test in which results are presented in terms of a rating, for example V0, achieved at a given thickness of test material. Several different material thicknesses can be used in the test, and it will be appreciated that where a V0 rating is achieved at one thickness this rating would also be attained if thicker test pieces were used. Materials which increase fire resistance or flame retardance, however, frequently degrade other properties of the composition, including strength properties. This can be a particular challenge where the application requires thin wall structures which are harder to attain flame retardance for in the first place, and which are more susceptible to failure as a result of mechanical strength. Thus, specific compositions with good flame retardance even in thin wall structures which retain mechanical strength are desirable.